Thermoset polymers have distinct advantages over thermoplastic polymers in may situations. For example, thermoplastics are not readily amenable to filling with glass or carbon fibers to produce composites. They also tend to have poor chemical and heat resistance and poor thermal stability. Thermoplastic polymers also tend to creep, which can be extremely undesirable in uses where very high tolerance is required. Thermoset polymers on the other hand tend to exhibit superior characteristics in all the foregoing as well as other physical and chemical properties.
A relatively new family of thermoset polymers is that comprising dicyclopentadiene monomer (DCPD). The homopolymer of DCPD is polydicyclopentadiene (pDCPD). While still a relatively new polymer, the physical and chemical properties of which have not as yet been fully explored, it is already exhibiting impressive properties with regard to, for instance, very high impact resistance, excellent chemical corrosion resistance and a high heat deflection temperature.
Due to its outstanding properties, pDCPD already has many uses, for example as vehicle parts, dish antennas and storage tanks for hazardous chemicals. While many fabrication techniques may be employed with pDCPD, reaction injection molding (RIM) is the technique most frequently used. In this method, DCPD and a curing catalysts are injected into a mold and left there until polymerization is complete.
PDCP used in RIM is generally of relatively low purity, in the mid 80% range for the most part. It has been found, however, that constructs formed of high purity DCPD—92% or higher—tend to display superior properties to constructs made of lower purity DCPD. The problem is that the higher purity DCPD tends to be very viscous, at least at temperatures below 100° F., and therefore must generally be heated in order to render the prepolymer formulation flowable for use in RIM processing. Not only does the necessity for heating the high purity DCPD detract from the economical aspects that makes its use desirable, it also presents a problem with regard to curing in that such may occur too rapidly resulting in partially formed constructs or constructs containing structural flaws. Thus, while the properties of pDCPD formed from high purity DCPD are most desirable, to date nothing has been done to ameliorate the foregoing and make use of the high purity DCPD more feasible.
What is needed, then, is a prepolymer formulation comprising high purity dicyclopentadiene that is amendable to use in a wide variety of construct fabrication processes, in particular economical processes such as RIM that may be used at ambient temperature (and lower) fabrication and cure conditions. The present invention provides such a formulation.